Regarding a conventional engine valve actuating device, there is known a device as described, for example, in a document of JP-A 4-72403. The outline will be described. A rocker arm for opening and closing an intake valve or an exhaust valve is swingably supported by a rocker shaft, and two sub-rocker arms are arranged on the same axis as the rocker shaft and in parallel, which come in slide contact with low-speed and high-speed cams in the engine operating state, respectively. Moreover, a selectively connecting mechanism is arranged for selectively connecting said two sub-rocker arms to the rocker shaft.
Said selectively connecting mechanism is provided with a connecting plunger arranged in the rocker shaft along its radial direction, and a hydraulic circuit for selectively supplying a working hydraulic pressure to the connecting plunger. When the connecting plunger is in engagement with a through hole of the sub-rocker arm by a working hydraulic pressure, the sub-rocker arm is in connection with the rocker shaft.
Moreover, when the connecting plunger is in non-engagement with the through hole of the sub-rocker arm, the sub-rocker arm is in non-connection with the rocker shaft.
In such selectively connecting mechanism, since one end of the connecting plunger arranged in the rocker arm is selectively engaged with the through hole of the sub-rocker arm, it is limited to set to a large value the diameter of the connecting plunger in the rocker shaft having a predetermined diameter due to a problem of the mechanical strength. Moreover, it is necessary to increase the accuracy of engagement of the outer peripheral surface of the connecting plunger with respect to the through hole of the sub-rocker arm. As a consequence, there arises a problem to fail to achieve an improvement in wear resistance of the connecting plunger and a sufficient reduction in manufacturing cost thereof.
Regarding an improvement proposal in such a case, as shown in JP-U 6-073301, in place of arranging the connecting plunger in the rocker shaft, one lever member as a connecting member and corresponding to each sub-rocker arm is rotatably supported by the rocker arm, and is disposed along the center axis of the rocker shaft, wherein when one end of each lever member is selectively in engagement with an engaged portion of the corresponding sub-rocker arm, the lift characteristic of an intake valve or an exhaust valve swung by the rocker arm is varied.
However, as described above, since one lever member as a connecting member and corresponding to each sub-rocker arm is rotatably supported by the rocker arm, and is disposed along the center axis of the rocker shaft, there is a limit to a relative reduction in the width of rocker shaft in the selectively connecting mechanism.
Taking account of the above problem, the present invention aims to provide engine valve actuating devices that can switch the valve-lift characteristic in three steps in accordance with the engine operating state, and that allow a reduction in size of a selectively connecting mechanism.